[Chemical and traumatic irritation of a canine premolar tooth germ]

The arrest of a premolar bud was observed in an animal experiment that was designed to study the influence of endodontic treatment in dogs' temporary teeth on the eruption of their permanent successors. A chemical irritation was induced by the burst of ZOE (zinc oxide and eugenol) into the dental follicle. Moreover, a mechanical trauma on the temporary molar was promoted by the dog's biting on its cage metallic bars. The devitalization effects were studied in thick undecalcified ground sections which were subjected to microradiographic analysis, to UV light microscopy in order to detect the fluorescent indicators of calcification, and finally to methylene blue staining. The arrest of the bud development was noted in fluorescent microscopic examination. Cellular cementum was formed on the pulpal surface of the dentine, while cementum, chondroid tissue, woven bone and lamellar bone developed in the pulpal tissue. These observations advise caution during root canal therapy of temporary teeth, especially those that are exposed to mechanical trauma. Such as the upper incisors.